1. Field of the Invention
The present invention relates to a method for forming a photoresist pattern, a method for forming a capacitor electrode using the same and a capacitor. More particularly, the present invention relates to a method for forming a ring-type photoresist pattern having an open bottom face and an open upper face, a method for forming a capacitor using the same, and a capacitor manufactured by using the ring-type photoresist pattern.
2. Description of the Related Art
For functionality, semiconductor devices require fast operation and high accumulation capacity. For this purpose, manufacturing technologies for improving integration density, response speed and reliability are being developed.
Dynamic random access memory (DRAM) is widely used as a semiconductor device that can input and output information. A DRAM has a cell region for storing information data in the form of electrons and a peripheral circuit region for transferring information data to or from the cell region. A DRAM device typically includes one access transistor and one storage capacitor.
As the degree of integration of semiconductor devices increases, it becomes difficult to improve the capability of a capacitor because the horizontal area that the capacitor occupies decreases. To increase the storage capability of a capacitor, a method for increasing an efficient area of the capacitor has been developed. According to the method, the structure of a capacitor is varied from a planar structure to a stacked structure or a trench-type structure. A stacked capacitor may be further varied to have a cylindrical structure to increase the effective area of the storage electrode.
Other structures for increasing the capacitance of a capacitor include a stacked capacitor having a crown shape, a stacked capacitor having a pin shape, and a capacitor having hemispherical silicon grains formed on a storage electrode thereof.
However, according to conventional methods for forming capacitors, additional processes may be necessary to vary the structure of a capacitor, thereby complicating the method for manufacturing the capacitor.
To grow the hemispherical silicon grains on the storage electrode of the capacitor mentioned above, a sufficient interval between storage electrodes is necessary to prevent a bridge between the storage electrodes. However, to realize a more highly integrated semiconductor device, a design rule thereof has been reduced, and an interval between storage electrodes of the semiconductor device has become even more miniscule. As a result, there may be a limit for growing hemispherical silicon grains on storage electrodes.
FIGS. 1A to 1D illustrate cross sectional views depicting a conventional method for forming a cylindrical capacitor.
Referring to FIG. 1A, a first insulation film 12 is formed on a semiconductor substrate 10, and a contact plug 14 making contact with the semiconductor substrate 10 is formed at a predetermined portion of the first insulation film 12.
An etch stop film 16 is formed on the first insulation film 12, and a second insulation film 18 is formed on the etch stop film 16.
Referring to FIG. 1B, an opening 20 exposing an upper portion of the contact plug 14 and a portion of the first insulation film 12 is formed by successively etching predetermined portions of the second insulation film 18 and the etch stop film 16 to make a second insulation film pattern 18a and an etch stop film pattern 16a. 
A polysilicon film having a uniform thickness is formed on a sidewall and a bottom face of the opening 20, and on an upper face of the second insulation film pattern 18a. A sacrificial layer (not shown) is formed on the polysilicon film to fill the opening 20 having the polysilicon film formed thereon, and an upper portion of the sacrificial layer is planarized by an etch back process to separate the polysilicon film into a storage node. The sacrificial layer is removed to form storage node electrode 22, as shown in FIG. 1C.
Referring to FIG. 1D, a capacitor is completed by forming a dielectric film 24 and a plate electrode 26 on the storage node electrode 22.
In the method described above for manufacturing a cylindrical capacitor, complicated manufacturing processes including a deposition process for the insulation films, an etching process, a deposition process for the polysilicon film, a deposition process for the sacrificial layer, and a separation process for the storage node are performed to form the cylindrical storage node electrode node. Therefore, processing failures may occur during any of the complicated processes, and a productivity of the capacitor may be reduced.
In an attempt to solve the problems mentioned above, a method for forming a semiconductor device using a phase shift mask has been proposed. However, according to the method, the height of a storage node electrode may not be increased because the low structure of the storage node electrode may be unstable. In addition, with the phase shift mask, the phase of light passing through a phase inversion material of the phase shift mask may not be inverted so that the light passing through the phase inversion material has an intensity identical to that of light passing through an open region of the phase shift mask.